meta: FIX sfinae idiom in use_* aliases

include/utl/meta/if.h

@@ -53,10 +53,6 @@ namespace utl {
    template<typename _Tp>  // Partial specialization for false.
    struct if_ <false, _Tp> { };
 
-   //! Alias template for if_
-   template<bool _C, typename _Tp = void>
-   using if_t = typename if_<_C, _Tp>::type;
-   //! @}
 }
 
 //! @}

include/utl/meta/sfinae.h

@@ -54,71 +54,34 @@ namespace utl {
    using void_t = typename void_t_impl<_Ts...>::type;
    //! @}
 
+   //! Alias template for if_
+   template<bool _C, typename _Tp = void>
+   using if_t = typename if_<_C, _Tp>::type;
+
+   //! Publicly recognized alias template for if_
+   template<bool _C, typename _Tp = void>
+   using enable_if_t = typename if_<_C, _Tp>::type;
+
+   //! Uniform alias template for if_
+   template<bool _C, typename _Tp = void>
+   using use_if_t = typename if_<_C, _Tp>::type;
 
    //! If same type resolves to _Ret, else SFINAE
-   //! @{
    template <typename _T1, typename _T2, typename _Ret =_T1>
-   struct use_if_same_ {
-      using type = if_t <
-                      same_<_T1, _T2>::value,
-                      _Ret
-                   >;
-   };
-   template <typename _T1, typename _T2, typename _Ret =_T1>
-   using use_if_same_t = typename use_if_same_<_T1, _T2, _Ret>::type;
-   //! @}
-
+   using use_if_same_t = typename if_<same_<_T1, _T2>::value, _Ret>::type;
 
    //! If not same type resolves to _Ret, else SFINAE
-   //! @{
-   template <typename _T1, typename _T2, typename _Ret =_T1>
-   struct use_if_not_same_ {
-      using type = if_t <
-                      !same_<_T1, _T2>::value,
-                      _Ret
-                   >;
-   };
    template <typename _T1, typename _T2, typename _Ret =_T1>
-   using use_if_not_same_t = typename use_if_not_same_<_T1, _T2, _Ret>::type;
-   //! @}
-
+   using use_if_not_same_t = typename if_<!same_<_T1, _T2>::value, _Ret>::type;
 
    //! If any type (_T1 or _T2) type resolves to _Ret, else to SFINAE
-   //! @{
-   template <typename _T1, typename _T2, typename _Ret =_T1>
-   struct use_if_any_ {
-      using type = if_t <
-                      or_<_T1, _T2>::value,
-                      _Ret
-                   >;
-   };
    template <typename _T1, typename _T2, typename _Ret =_T1>
-   using use_if_any_t = typename use_if_any_<_T1, _T2, _Ret>::type;
-   //! @}
-
+   using use_if_any_t = typename if_<or_<_T1, _T2>::value, _Ret>::type;
 
    //! If both type (_T1 and _T2) type resolves to _Ret, else to SFINAE
-   //! @{
    template <typename _T1, typename _T2, typename _Ret =_T1>
-   struct use_if_both_ {
-      using type = if_t <
-                      and_<_T1, _T2>::value,
-                      _Ret
-                   >;
-   };
-   template <typename _T1, typename _T2, typename _Ret =_T1>
-   using use_if_both_t = typename use_if_both_<_T1, _T2, _Ret>::type;
-   //! @}
+   using use_if_both_t = typename if_<and_<_T1, _T2>::value, _Ret>::type;
 
-   //! Publicly recognized alias template for if_t
-   template<bool _C, typename _Tp = void>
-   using enable_if_t = typename if_<_C, _Tp>::type;
-
-   //! Uniform use_ style alias template for if_t
-   //!@{
-   template<bool _C, typename _Tp = void>
-   using use_if_t = typename if_<_C, _Tp>::type;
-   //!@{
 }
 
 //! @}